Conclusion: Congenital hypothyroidism in Iran may have different etiologies. Due to higher rate of transient CH than other similar researches, it is reasonable to ...
Iran J Pediatr Jun 2011; Vol 21 (No 2), Pp: 188-192
Original Article
Does Congenital Hypothyroidism Have Different Etiologies in Iran? Zohre Karamizadeh1, MD; Setillia Dalili1, MD; Heidyeh Sanei-far1, MD; Hamdollah Karamifard1, MD; Hamid Mohammadi2, MD, and Gholamhossein Amirhakimi1, MD 1. 2.
Pediatrics Endocrinology Division, Nemazee Hospital, Shiraz University of Medical Sciences, Shiraz, Iran Department of Pediatrics, Nemazee Hospital, Shiraz University of Medical Sciences, Shiraz, Iran Received: Feb 15, 2010; Final Revision: Oct 05, 2010; Accepted: Dec 26, 2010
Abstract Objective: To determine the prevalence of congenital hypothyroidism (CH), permanent and transient CH.
Methods: From November 2006 to September 2007, 63031 newborns were screened by measuring serum TSH obtained by heel prick. The neonates who had a TSH≥5mU/L were recalled for measurement of serum T4, thyroid stimulating hormone (TSH) and TSH receptor blocking antibodies (TRBAb) in venous samples. In 43 primarily diagnosed as cases of CH, treatment was discontinued at age 2-3 years for 4 weeks and T4 and TSH were measured again. Permanent or transient CH was determined from the results of these tests and radiologic evaluation.
Findings: The incidence of congenital hypothyroidism was found to be 1:1465 with a female to male ratio of 1.19:1. The most common clinical findings were prolonged jaundice (73%), large anterior fontanel (56%) and wide posterior fontanel (55%). In 43 patients with CH, prevalence of permanent and transient form of the disorder was 53.6% and 46.4% respectively. Permanent CH was associated with higher initial TSH level than transient hypothyroidism (P6 mU/L after 4 weeks of levothyroxine discontinuation were diagnosed as a permanent congenital hypothyroidism. TSH receptor blocking antibody was also measured in all mothers during follow up period. TSH was measured by immunoradiometric assay (IRMA) (Xit Immunotech, Belgium). T4 was measured by radioimmunoassay (RIA) (Immunotech, Blegium) and TRBAb by Elisa (Diametera, Italy) and TRBAb values greater than 1.5 /l were considered abnormal.
Findings Between November 2006 and September 2007, a total of 63,031 neonates were screened in Fars province and 127 neonates (about 1:500 of screened neonates) with an abnormal screening result were referred to the pediatric endocrinology clinic. In 43 cases, CH was diagnosed with a prevalence of 1:1465. Sex distribution of
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Etiology of Congenital Hypothyroidism in Iran; Z Karimzadeh, et al
Table 1: Sex distribution of congenital hypothyroidism Congenital Hypothyroidism
Sex Female Male Total
Permanent (% of total CH) 13 10 23 (53.6)
these 43 patients was 51% (22 cases) females and 49% (21cases) males (table 1). Regarding the total number of screened females and males, the incidence of CH was 74 and 64 in 100000 births respectively. The clinical findings included: 31 (73.1%) neonates with CH had a history of prolonged jaundice, 5 (11.6%) an umbilical hernia, 23 (55%) large posterior fontanel (>0.5 cm) and 24 (56%) large anterior fontanel (larger than 2.5×2.5). None of the patients had a history of CH or thyroid disease in his/her mother or siblings. Parental consanguinity was present among 34.1% of confirmed congenital hypothyroidism patients. The incidence of permanent and transient hypothyroidism was 53.6% (23 cases) and 46.4% (20 cases) respectively according to the scintigraphic and/or ultrasonographic findings. Among 20 patients with transient CH, 7 patients had elevated TSH level and normal T4 (“isolated hyperthyrotropinemia”).
Chart 1: Etiology of Congenital Hypothyroidism in Shiraz, Iran Study. Thyroid agenesis includes agenesis or hypoplasia. TRBAb: TSH receptor Blocking Antibody.
Transient (% of total CH) 9 11 20 (46.4)
Total (% of total CH) 22 (51) 21(49) 43
All patients with transient CH had normal thyroid glands and in permanent CH 13 cases (57%) had dyshormonogenesis, 10 cases (43%) had thyroid dysgenesis (9 cases of agenesis or hypoplasia and 1 case of ectopia). The mean TSH values in transient CH were significantly lower than those in patient with permanent CH (27.2 versus 60.3 with P value
